Insulin-like growth factor-1 elevated in hypertensive patients

Abstract

Insulin-like growth factor-1 (IGF-1) is a single-chain peptide, which shares structural homology with pro-insulin. The majority of circulating IGF-1 originates in the liver and is regulated mainly by growth hormone (GH)(hypophysis-hepatic axis) but also by insulin and nutritional intake. GH and IGF-1 exert opposite effects on glucose metabolism. In the pathophysiology of essential hypertension there are structural changes that modify the wall-to-lumen ratio, termed vascular remodelling. Once endothelial dysfunction is established, smooth muscle cell proliferation ensues. Vascular hypertrophy associated with hypertension can also lead to the closure of small vessels and could therefore contribute to the increased vascular resistance in long-standing hypertension. Several growth factors such as FGF, TGF-b, and PDGF play an important role in this process. It is yet unknown if IGF-1 contributes in the same way. To evaluate circulating IGF-1 levels in a non selected population of hypertensive patients treated with antihypertensive drugs. To correlate them with systolic and diastolic blood pressure levels obtained by ambulatory blood pressure monitoring (ABPM). Study population: N=30 hypertensive patients, aged 38 to 77 years (60+-11), 15 males, 15 females, 14 type 2 diabetics. Anthropometric parameters: BMI (Kg/m2), waist circumference (cm). Biochemical parameters: Glycaemia, insulinaemia (uU/mL) - Immunometric assay. Immulite. DPC, insulin resistance (IR)(HOMA). HbA1c by HPLC. IGF-1 (ng/ml): 100 t kit. RIA: Nichols Institute Diagnostic. Hemodynamic parameters: 24-hour ABPM (90207spacelabs): systolic blood pressure (SBP), diastolic blood pressure (DBP) and mean blood pressure (MBP). Statistical analysis: Chi-square, linear regression. IGF-1 levels did not correlate with age, gender, type 2 diabetes mellitus, insulinaemia, IR, or HbA1c. There was an excellent correlation between IGF-1 and average DBP (r=0.4; p=0.019). The hypophysis-hepatic axis could contribute to blood pressure control. This phenomenon is not related to insulin resistance.